2018 Mercedes-Benz S-Class: 48-volt system is the future, but diesel’s not dead yet

With the recent resurgence of petrol engines – thanks largely to the efficiency and power delivered by turbo technology – and the addition of high-capacity mild hybrid systems like the 48V battery system used in the facelifted, 2018 Mercedes-Benz S-Class (among others), you could be forgiven for thinking the bell is about to toll for the diesel engine.

But, despite the petrol engine making serious strides forward, the diesel engine will be around for a while yet, according to Mercedes-Benz engineers at the recent S-Class international drive programme in Zurich. That commitment also comes on the back of the brand confirming the voluntary recall of up to three million vehicles in Europe to comply with emissions ratings.

Powertrain development leader Armin Herold is both an avid internal combustion fan, and one such engineer, who sees a positive future for diesel engines.

“The diesel engine definitely has a future and we have a new engine with the best technology for a clean exhaust,” Herold told Australian media in Zurich. “We believe this can have a strong future to meet regulations around the world for the future. It is a big investment for us.”

The diesel engine we tested in the revised S-Class is among the most advanced of its platform from any manufacturer. It generates ten per cent more power, yet emits seven per cent less exhaust nasties than the V6 diesel it replaces.

The 350d and 400d variants in the S Class range feature the diesel engine in two different states of tune with both claiming to use less than 6.0L/100km on the combined cycle.

Herold did admit that the 48V system – used on the new inline six-cylinder petrol engine – could be adopted for the diesel engine to make it even cleaner and more efficient, but reiterated that the benefits are not as broad as the petrol engine.

What the 48V system primarily allows is faster and more efficient start up, as well as a beltless engine design. The power steering pump, the AC compressor and the water pump, are all powered by the 48V system directly, and the alternator is mounted directly off the crank, so there are no ancillaries run by belts like a traditional engine.

Pushed on whether the internal combustion engine is going to disappear in the near future, Herold was resolute.

“I think the combustion engine is not dying. Nobody knows the full transition to electric engines just yet. There is also the question of the investment to have sustainable energy that marks it truly zero emissions.”